The heart of a computer is a magnetic hard disk drive (HDD) which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
The volume of information being processed and stored on HDDs is increasing rapidly. In particular, HDDs have been used to store more and more information, while remaining within their limited area and volume.
A recording medium having a large coercive force (namely, a large magnetic anisotropy) must be used in magnetic recording in order to stably maintain the recording magnetization state. However, this results in the need to use a strong recording magnetic field to record on any recording medium that has a large coercive force. In practice, magnetic materials which may be used as materials for construction of a magnetic head are limited. Consequently, the coercive force of the recording medium is constrained by the magnitude of the recording magnetic field which may be generated by the recording head using available magnetic materials.
Therefore, in some previous attempts to overcome these problems, a recording method has been used which takes advantage of various compensation methods, causing the coercive force of the recording medium to be effectively lowered only during recording. A representative example is a system which uses heat-assisted recording, which has a heating element, such as a laser, that locally heats the recording surface of the magnetic medium during recording, thereby reducing the coercive force of the recording medium so that data may be recorded.
Conventionally, in order to improve the magnetic recording density, the magnetic recording width, measured as tracks per inch (TPI), and the linear recording density, measured as bits per inch (BPI), were narrowed. To narrow the magnetic recording width, the width of the main pole (main magnetic pole) is narrowed, but the magnetic field strength drops when the width of the main pole becomes narrow, and improving the recording width density becomes difficult. In addition, since the main pole has a complex structure, the fabrication error becomes large when a narrow magnetic recording width is created, and the number of heads having a magnetic recording width, which is the target, tends to be few.